Rare Microsporidiosis Infections Found in Organ Transplant Recipients

Approximately 30,000 solid organ transplants are performed each year in the United States. Donor-derived infections complicate up to 2.0% of these transplants, and typically involve bacterial or viral infections. Parasitic and fungal infections comprise only a minority of these infections.

Microsporidiosis is a disease caused by infection with microsporidia, which are spore-forming fungal organisms. It has been associated with immunosuppression, especially in HIV patients before the advent of antiretroviral therapy, and now increasingly occurs in transplant recipients. Typically, microsporidiosis causes gastrointestinal disease with diarrhea and malabsorption. However, disseminated disease can also occur, and often involves the urinary tract.

Rachel M. Smith, MD, from the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and colleagues recently described a rare presentation of disseminated microsporidial infection that was transmitted to three solid organ transplant recipients from a single infected donor.

In April 2014, CDC investigated the case of a kidney transplant recipient who died after experiencing signs and symptoms of encephalitis. Postmortem examination and testing identified microsporidial organisms in the kidney graft. The investigators were concerned that this infection may have originated in the organ donor, and ultimately determined that a total of three patients had received four organs (kidney; liver; heart and kidney) from the same donor.

The patient who received the heart and kidney transplant had also been hospitalized with encephalitis, while the liver transplant patient experienced tremor and gait instability. “None experienced gastrointestinal symptoms,” the authors note.

Diagnostic testing showed that Encephalitozoon cuniculi caused the infections in all three patients. The organ donor was a middle-aged woman who had lived in the United States for several decades, but was originally from Mexico. She had developed neurological symptoms in December 2013, which she initially suspected were due to migraine. However, the symptoms persisted for several weeks, and she eventually received medical care at an emergency department, where clinicians found that she had arteriovenous malformations and an internal carotid aneurysm. She underwent surgery, but her neurological symptoms progressed, and she was eventually declared brain dead. She had no recent history of gastrointestinal disease, and no other known risk factors for microsporidiosis.

In an interview with Contagion^®, Dr. Smith emphasized that this investigation was deemed a public health emergency. “CDC began investigating because there was an ill organ transplant recipient, and there was concern that the illness was an infection that might be been transmitted from the organ donor to the recipient,” she said.

Dr. Smith added that understanding whether this type of infection is donor-derived is an emergency because it has serious implications for all the recipients of organs from the potentially infected donor.

According to Dr. Smith and colleagues, the three transplant recipients experienced an extremely rare presentation of microsporidiosis that manifested as neurologic disease without any gastrointestinal signs and symptoms.

She stressed that clinicians should consider microsporidiosis as a differential diagnosis when they are managing immunocompromised patients with symptoms suggestive of encephalitis, even in the absence of gastrointestinal signs or symptoms. Although donor-derived infections are relatively rare, she added that clinicians should evaluate any organ transplant recipient with an infection for the possibility that the infection originated in the donor.

“Clinicians should maintain a high index of suspicion for donor-derived infections and should report any suspected or potential events to the Organ Procurement and Transplantation Network,” she concluded.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.